Char length in Arduino sketch

Question

I have the following char inside an Arduino sketch:

char inData[80];

When I print to the serial console:

Serial.print(strlen(inData) - 1);

I'm expecting to see: 79 instead I see: 655356553501234567

Can someone shed some light as to why this is happening?

Answer 1

strlen is looking for a terminating nul. Calling it on an uninitialized array or pointer results in undefined behavior. You want sizeof(inData) instead.